Texas Instruments 990 User Manual page 237

Communications Structures
* Reset request (RQ) packet
*
Reset confirmation (RC) packet
*
Receive ready (RR) packet
*
Receive not-ready (RNR) packet
*
Data packet
0.3.1 Reset Request Packet
A reset request packet is transmitted when any of the following
occur:
*
An invalid packet send count, peS), is found in a data
packet.
*
An invalid packet receive count, peR), is found in data
packet, an RNR packet, or an RR packet.
*
*
*
*
An incorrect packet length is detected.
The general format identifier is not 0001.
Multiple retransmission attempts result in failure.
A time-out occurs after sending a reset request.
Normally, the secondary station sends an RQ packet and
then awaits a reset confirmation packet. If the reset
confirmation packet is not detected within a pre-
determined time the RQ packet is retransmitted.
Transmission of the RQ packet is repeated until either a
reset confirmation or an RQ packet is received. In
either event the reception is treated as a reset
confirmation since both stations are apparently
attempting to reset.
The following conditions are ignored
by
the packet level and do
not require reset action:
*
Reception of a packet with an invalid LCI.
*
Reception of a packet of unknown type.
When a reset request packet is transmitted the following events
should occur:
*
The packet level send counter, peS), is set to zero
*
The packet level receive counter, peR), is set to zero
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